try
{
  ServerSocket s = new ServerSocket(1234);  // Create server
  while (true)
  {
   Socket c = s.accept();        // Await connection
   InputStream i = c.getInputStream(); // Get input stream
   OutputStream o = c.getOutputStream();//Get output stream
   do
   {
     byte[] line = new byte[100];   // Create scratchpad
     i.read(line);        // Read client's message
     o.write(line);            // Send it back
   }
   while ( !str.trim().equals("eof") );
   c.close();              // Close connection
  }
}
catch (Exception err)
{
  System.err.println(err);
}

Socket s = new Socket("192.168.1.1", 123);   // Create socket
InputStream i = s.getInputStream();    // Get input stream
OutputStream o = s.getOutputStream();   // Get output stream
String str;
do
{
  byte[] line = new byte[100];
  System.in.read(line);                 // Read from console
  o.write(line);                        // Send the message
  i.read(line);                         // Read it back
  str = new String(line);               // Convert to string
  System.out.println(str.trim());       // Print message
}
while ( !str.trim().equals("bye") );
s.close();                 // Close connection